Willow Brook Catchment Project

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Audrey Chapman
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1 Willow Brook Catchment Project Willow Brook Park Page 1

2 Contents 1. Introduction Background The Water Framework Directive and Drivers for Change The Willow Brook Catchment and Water Framework Status Willow Brook Park Reasons for the Project Key Themes Aims and Objectives Aims of the Project Objectives of the Project Benefits of the Project 7 3. The Project Area 1 Naturalise brook flood relief basin Area 2 Re-instatement of Wetland and Access Area 3 Access - Pathways and Scrapes Area 4 Naturalise water course Bushby Brook Costs Constraints and Timing. 15 Page 2

3 1. Introduction 1.1 Background The Water Framework Directive and Drivers for Change The Water Framework Directive (WFD) introduces an holistic approach to the management of water quality and establishes a system to protect and improve all aspects of the water environment which includes rivers, brooks, lakes, other open waters and groundwater. The Directive requires some inland and coastal waters reach good status by Those water bodies classified as artificial or heavily modified because they have been created or modified to support uses such as water supply, flood protection, navigation or urban infrastructure have lower targets and need to reach good ecological potential by The good status set by the WFD is set by a series of biological, chemical, physical (including hydromorphology) elements. Much of the work to implement the Directive is undertaken by Competent Authorities which include the Environment Agency, but achieving this target requires management planning at river basin level and greater public and local involvement to determine the design, management and maintenance of our water courses. Local Authorities are required to have regard to the River Basin Management Plan and supplementary documents. A wide variety of pressures on the water environment can cause waterbodies to deteriorate to less than good status. Examples of such pressures include point source pollution such as effluent discharging from industrial sites and combined sewer overflows; and diffuse pollution which can be caused by past and current land use in agricultural and urban environments. In urban areas such as those of found in Leicester this could include urban diffuse pollution from sources such as runoff from impermeable surfaces (e.g. highways), sediment runoff from land under construction, drainage misconnections, spillages and poor storage, litter and runoff from contaminated land. Physical modifications through straightening and impounding structures are widespread, localised flooding and habitat degradation from man-made impacts such as invasive non-native species dominating and out-competing native species and/or causing physical damage to structures e.g. through rampant, unchecked Japanese Knotweed, Floating Pennywort, Giant Hogweed, American Signal Crayfish. Page 3

4 1.2 The Willow Brook Catchment and Water Framework Status The Willow Brook Catchment (33.9 km 2 ) has a distinct rural land use upstream and a heavily urbanised catchment downstream. The catchment area includes the Scraptoft Brook, Evington Brook, Thurnby Brook and Bushby Brook which originate at a number of rural locations before flowing though into the city and eventually converging to form the Willow Brook. The brooks within the Willow Brook catchment flow in an east-west direction towards the City centre and confluence with the River Soar. The urban catchment area within the Leicester boundary is typical of a large city and is made up of a dense infrastructure of housing, schools, employment areas and green space through which an established road network facilitates access. The watercourses are heavily engineered and mainly contained in concrete channels or underground culverts as a result of historic flood defence programmes constructed in the 1970s. The water courses emerge in areas of green space used for sports, education and recreation within the City s Parks and School grounds. Overall status of the watercourse is moderate and at risk. This is based on the ecological, physical, chemical and biological elements of the water body stretches that make up the Willow Brook catchment. The hydro-morphological status of the water bodies is heavily modified. The failing elements of the water bodies are related to the structure of the watercourses, phosphates and invertebrates. The failures are associated with the physical modification of the water courses, and the number and range of diffuse and point pollution sources. These include Phosphates entering the water from intermittent sewage discharge, drainage and diffuse runoff from urban environments as well as runoff from rural land associated with agricultural use. A summary of the section of water body is provided below which shows the reasons for failure. Table 1.1: Willow Catchment Water Bodies and Reasons for Failure under Water Framework Directive Page 4 Water Body Stretch Ecological Status Chemical Status Physical Status Willow Brook from Evington Brook to River Soar GB Moderate due to impacts from specific pollutants e.g. Triclosan (fail) Moderate significant risk to or via aquatic environment at Community level and include priority hazardous substances, issues with Phosphates Heavily modified hydromorphology water largely enclosed in concrete channels and culverts

It has close community links with several primary schools located on the boundaries of the park, together with Community facilities facing onto the green space made up of several small shops, a pub

5 1.3. Willow Brook Park Willow Brook Park is a popular and well-used park located to the east of the City in a largely residential area. The Park is part of an extensive linear area of green space through which the Bushby and Thurnby Brook flow and forms part of the Willow Brook catchment. It has close community links with several primary schools located on the boundaries of the park, together with Community facilities facing onto the green space made up of several small shops, a pub and social club/community centre. The Park has been created from previous landfill capped over and as a result of land excavations to create major flood defence works in the past. As a result the site is effectively a basin that provides flood storage through which the brook flows. Access for park users is via a series of stone pathways or desire line footpaths. It provides the link between the wider rural area outside of the City where the brook is more natural to a more urban and managed environment where the brook is contained within steep-sided channels and heavily-engineered structures restrict the flow Reasons for the Project The Bushby Brook and Thurnby Brook converge in the upper section of Willow Brook Park before joining and continuing as the Bushby Brook. The brooks are contained largely within earth banks, some of which are steeply graded but other sections are more open with shallow gradients. This area is a mix of semi-natural green space to the west and a more formal park and amenity area to the east. The site provides an important flood management area with green space and has a marshy wetland and willow carr area to the east that has largely been left un-managed for a number of years. To the east the brook flows through a more formal area of the Park and through steep earth banks where it remains largely hidden. Page 5

6 The brook has been heavily engineered and has a large weir in the central part of the site. The weir functions to slow water flow and aerate the watercourse, but there are several sections of the brook where sediment settles out and encourages the build-up of vegetation and potential blockages. This has resulted in engineering, dredging and clearance works by the EA in the last five years to facilitate flow, but a more sustainable solution is sought to deal with the issues. The key themes are listed below and are strongly linked to tackling urban diffuse pollution and improving the overall status of the Willow Brook by dealing with some of the reasons for failure identified by the Water Framework Directive indicators Key Themes WFD/Urban diffuse pollution Biodiversity/conservation Recreational/amenity Flood risk management Climate change Education Page 6

7 2. Aims and Objectives 2.1 Aims of the Project To implement a series of sustainable measures that will improve the water environment and Water Framework Directive (WFD) indicators whilst providing additional environmental benefits to local residents and wildlife 2.2 Objectives of the Project Improve the hydro-morphology of the watercourse by breaking out and removing concrete channels; Improve water quality and flow rates by intercepting runoff and creation of on and off-line SuDs within the brook and filtrate through vegetation; Improve the ecological status/biodiversity value by planting-up the floodplain and brook; Improve visual amenity and encourage use of the Park though appropriate design, landscaping and planting; Raise local awareness and appreciation of the Brook by creating a more natural, safe and attractive environment Commence monitoring scheme on the Brook to measure local water quality indicators 2.3 Benefits of the Project Reduce diffuse urban pollution from adjacent land into the Brook by using natural features/vegetation as SuDs to intercept runoff, rainfall; Address WFD failures by improving hydro-morphology of the channel and improve chemical, physical and biological indicators through infiltration processes and reducing flow rates; Reduce flood risk further downstream by slowing flow rates and increasing water storage capacity on site - provide benefits downstream in the larger Soar catchment; Create habitats to enhance biodiversity and support species through the design and creation of pools and riffles within water channel and links to on and off-line open water areas which will provide a mosaic of habitats for wildlife associated with flowing and still water; Raise awareness of the brook by integrating it more in the Park and creating an attractive meandering water course which is safe and open. This will encourage better use of the Park (linked with public health and well-being) and make people more aware of the wildlife associated; Page 7

Access to the brook will be improved by the creation of shallow and safe gradients, planting and installation of a dipping platform to encourage public to have access; education and learn about water

8 Access to the brook will be improved by the creation of shallow and safe gradients, planting and installation of a dipping platform to encourage public to have access; education and learn about water and the wildlife associated with it Design landscaped areas and encourage public involvement in their design and planting schemes and management. Landscaping can be partly designed up by the public who can take part in planting and maintaining the brook (although still remaining the responsibility of the local authority). Overview Note: The Project does not include major engineering works to structures such as the large weir at the confluence of the Bushby Brook and Thurnby Brook. Such schemes would require significant planning, costs and be led by the Environment Agency and are beyond the remit of this Project. Page 8

3. The Project This Project is divided into a series of smaller-scale projects that make up a larger project. Appendix 1 shows the location of the Projects identified 3.

The adjacent area is floodplain and provides a mosaic of habitats.

9 3. The Project This Project is divided into a series of smaller-scale projects that make up a larger project. Appendix 1 shows the location of the Projects identified 3.1 Area 1 Naturalise brook flood relief basin Reasons for Project: The brook is largely contained within a linear channel to the north part of the basin. The adjacent area is floodplain and provides a mosaic of habitats. Biodiversity is present but limited in the current channel structure with areas of sediment build-up, causing nutrient enrichment and vegetation that restricts channel flow and requires regular maintenance Solution: Break out banks along the brook and provide soft edge to channel avoid culverted area under Dakyn Road Create series of pools and riffles via meanders and structures to aerate flow, provide micro-habitats and improve visual amenity Plant areas with native aquatic species Page 9

3.2 Area 2 Re-instatement of Wetland and Access Reasons for Project: Wetland marsh, willow carr contained within grassy banks provide a habitat in decline due to poor access and

The natural filtration processes are limited as the brook is off-line from the flood basin.

sizes and depths to create areas of permanent open water, ephemeral areas to enable natural filtration and improve water quality/biodiversity Thin out willow carr, retain wood

10 3.2 Area 2 Re-instatement of Wetland and Access Reasons for Project: Wetland marsh, willow carr contained within grassy banks provide a habitat in decline due to poor access and difficulty to maintain. The area is not accessible to the public for large parts of the year due to predominant wet conditions. The natural filtration processes are limited as the brook is off-line from the flood basin. Otters regular visit the site and spraint activity recorded but no habitat suitable for them to remain in the area Solution: Excavate out a series of wetland areas (4-6) of varying sizes and depths to create areas of permanent open water, ephemeral areas to enable natural filtration and improve water quality/biodiversity Thin out willow carr, retain wood on-site, create large log piles anchored into place and allowed to rot naturally Create otter holt from materials on site and/or EA otter holt pack Facilitate access across the area through a series of raised causeways, board walk and 2 x small footbridges Create small viewing/dipping platform for use by local schools Page 10

3.3 Area 3 Access - Pathways and Scrapes Reasons for Project: Access across the floodplain area is generally poor and difficult to manage

Encouraging better use of this area and creation of footpath linkages to a wider network of paths would encourage use as well as a safe environment

11 3.3 Area 3 Access - Pathways and Scrapes Reasons for Project: Access across the floodplain area is generally poor and difficult to manage effectively. This area leads to the more formal area of the Park and access from shops onto the Park. Encouraging better use of this area and creation of footpath linkages to a wider network of paths would encourage use as well as a safe environment or encourage public awareness of water quality and biodiversity. Solution: Re-profile scrape areas create 1 x larger scrape and deepen to below water table to facilitate some open water throughout the year Re-grade northern sloping bank to provide terraced level walkway at higher level for pedestrian access, compact surface, hard-core and re-seed Re-seed scrape banks with wet grassland seed mix Thin out plantation on top of north bank to encourage light and improve grassland diversity Page 11

12 3.4 Area 4 Naturalise water course Bushby Brook Reasons for Project: Hydro-morphology is a WFD failing indicator of the Willow Brook. The Thurnby Brook and Bushby Brook converge on this upper area of the Park, but are largely channelled through steep-sided earth banks before slowing to cascade over the weir. Regular build-up of sediment and maintenance/clearance around the weir area is required to facilitate flow and reduce flood risk. Major engineering/flood relief works may be planned in the future in this area, but these proposals provide a limited and cost-effective method of improving water quality and biodiversity at a localised level whilst maintaining flood resilience. Solution: Low-key re-grading of earth banks to create a series of shallow meanders; careful design to create to allow natural scouring and create a mini-riffle system to aerate flows and provide micro-habitat and improve visual amenity Create series of deeper pool areas to slow water flow in more accessible areas and provide areas for sediment to be removed Protect bank areas with aquatic planting to facilitate edge protection Page 12

13 4 Costs Area 1 Amount Unit Rate Cost Sub total Willow Brook Nature Area Naturalise brook Re-grade earth banks of brook 170 lin m Create pools and riffles in channel 40 m² Plant with marginal plants 60 m² Area 2 0 Re-instatement of wetland and access 0 Excavate 4 to 6 small wetland areas 70 m² Re-excavate ditch to link from brook into wetland and re-profile 36 lin m Thin-out willow carr plantation 30 m² Create otter holt 1 each Create boardwalk - recycled plastic 95 lin m Viewing/dipping platform 1 each Area Access to Pathways and Scrapes 0 Raised path on sloped bank - stoned surface- allow for regrade slope and form path 60 lin m Re-excavate and enlarge scrape 750 m² Re-excavate ditch to link from brook into wetland and re-profile 20 lin m Take off top soil and remove to agreed area outside floodplain 210 m² Thin-out plantation 125 m² Notes spoil to be kept on site spoil to be kept on site Page 13

14 conservation work to scrub 50 m² 0 Wildflower planting; wet meadow 150 m² Area 4 0 Naturalise Bushby Brook/Thurnby Brook 0 Break out banks along water course 75 lin m Create pools and riffles in channel 30 m² Plant with marginal plants 30 m² x day conservation work Page 14

15 5 Constraints and Timing Planning permission is unlikely to be required as this is dependent on the volumes of materials to be removed and any structural works (banks to be broken out in small sections to enable natural greening of edges only); Agreement from Environment Agency on proposed works and Panel Engineer if the site is considered to be a reservoir during flood conditions. The Panel Engineer will have to approve all works. Local Authority consents for works may be waived as on Local Authority land, but agreement is required Ecology the site is of ecological value see ecology report further surveys required during appropriate season Works proposed will require mitigation measures to minimise impact on watercourse and should take place outside of the bird nesting season (nesting season between March and end August) No trees are to be impacted by the proposed works All works should be scheduled in to cause minimal impact to wildlife Area 1 naturalise brook-flood relief basin works Area 2 Re-instate wetland and access see mitigation works and supervision required Area 3 Access to pathways see mitigation works and supervision required Area 4 and 5 Naturalise water courses further surveys required and see mitigation works and supervision required Page 15

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18 Extract from Ecology Survey Page 18

Application for resource consent Form B Damming and diversion of water

Application for resource consent Form B Damming and diversion of water Notes Resource use activities must meet all the conditions of any relevant Permitted Activity Rules in the Waikato Regional Plan or